As a device having a mechanism that handles components, such as electronic components, for example, many surface mounting machines and component testing machines have been proposed. In order to hold an electronic component, these machines are provided with a component holding member and it is possible to hold the component by sucking the top surface of the component at the lower end portion of the component holding member. Also, in order to transport a component from a component supply portion to a target position, the component holding member is incorporated into a head unit. In other words, the component holding member is moved to the target position by the head unit while it keeps holding the component. The positioning of the component at the target position is performed by releasing the component held by the component holding member at the target position. Hence, in order to increase the positioning accuracy, it is important to perform image recognition of a held condition of the component by the component holding member before the positioning so that the positioning of the component is performed by taking the held condition into account. In order to perform image recognition, the surface mounting machine and the component testing machine are equipped with a component recognizing device.
As such a component recognizing device, the one described, for example, in Japanese Patent No. 3186387 (paragraph [0017] and FIG. 3 and FIG. 4) has been known. According to this conventional device, a line sensor portion (corresponding to the scan unit of the invention) equipped with a line sensor is disposed below the component holding member so that an image of the bottom surface of a component can be taken by performing the scanning at the position directly below the component held by suction by the component holding member. A surface mounting machine equipped with this device is therefore able to enhance the positioning accuracy by performing image recognition of a held condition of the component according to the bottom surface image of the component.
Incidentally, the conventional device generally adopts a combination of a rotary motor (drive source), a ball screw shaft, and a ball and nut mechanism portion as a drive mechanism to drive the scan unit, such as the line sensor portion. In other words, a rotational drive force generated by the motor is converted to a linear drive force by the ball screw shaft and the ball and nut mechanism portion and the scan unit is driven using the linear drive force. This configuration raises a problem as follows in some cases.
As has been described, the component recognizing device takes an image of a component by moving the scan unit using the drive mechanism and the positioning of the component is performed according to the imaging result. Hence, in order to increase the positioning accuracy of the component, it is extremely important to position the scan unit at a high degree of accuracy and the drive mechanism is naturally required to have the positioning performance at a high degree of accuracy for the scan unit. However, the component recognizing device adopting the conventional drive mechanism has an error in the positioning accuracy of the scan unit in some cases because of wear of the ball screw shaft and the ball and nut mechanism portion.
As a countermeasure to solve the problems and issues as above, a linear motor may be employed as the drive source of the scan unit. The linear motor, however, drives an object to be driven (scan unit) using an interaction of magnetic fluxes generated by a stator and a mover while generating an attraction force between the stator and the mover. It is therefore necessary to apply the linear motor to the component recognizing device by taking the operating characteristics into account. More specifically, in a device adopting the linear motor, stress (attraction force) unique to the liner motor acts on guide means, such as a guide rail. Accordingly, in a case where the linear motor is improperly applied to the component recognizing device, excessively large stress may possibly be applied on the guide means and the components forming the guide means may wear out, which gives rise to rattling. Consequently, the position and the posture of the scan unit are changed and there is a possibility that image recognition of a component cannot be performed at a high degree of accuracy in a stable manner over a long term. In addition, in a case where a component recognizing device having poor stability and accuracy in image recognition as described above is incorporated into a surface mounting machine or a component testing machine, when the positioning of a component is performed according to the recognition result by the component recognizing device, the yield of the products is decreased and the inspection quality is deteriorated over a long term use.
The invention was devised in view of the foregoing and has a first object to perform the image recognition of a component at a high degree of accuracy in a stable manner over a long term with a component recognizing device configured to take an image of a component by moving the scan unit having imaging means.
Also, the invention has a second object to maintain a high mounting accuracy of a component on a substrate over a long term by increasing the image recognition accuracy of a component with a surface mounting machine equipped with a component recognizing device configured to take an image of a component by moving a scan unit having imaging means.
Further, the invention has a third object to maintain a component inspection accuracy over a long term by maintaining a high image recognition accuracy of a component over a long term with a component testing machine equipped with a component recognizing device configured to take an image of a component by moving a scan unit having imaging means.